The present disclosure relates to a method of distributing or commercializing a myoglobin-containing food product.
Meat appearance including color is an important quality characteristic of packaged meat products that affects their merchantability. Product packaging that preserves a desirable appearance and color of fresh meat can promote the merchantability and appeal of meat. Consumers often use color as an indicator of meat quality and freshness. Lighter colored meat is often easier to see than dark colored meat allowing a consumer to more easily differentiate meat surface characteriastics such as texture and marbling. The color of meat is related to the amount and chemical state of myoglobin in the meat. Myoglobin is present in the muscle tissue of all animals and functions to store and deliver oxygen by reversibly binding molecular oxygen, thereby creating an intracellular source of oxygen for the mitochondria. Pork and poultry typically contain lower amounts of myoglobin than beef and thus are lighter in color than beef.
Myoglobin includes an open binding site called heme that can bind certain small molecules, such as molecular oxygen (O2 or “oxygen”) or water. The presence and type of ligand bound at the myoglobin binding site can alter the color of the myoglobin. The color of the meat product will change based on the amount of myoglobin present and the amount and type(s) of ligand molecule(s) bound to the heme binding site. Myoglobin without a molecule bound to the heme site is a purple colored molecule called deoxymyoglobin. Molecular oxygen readily acts as a ligand that binds to the heme group, permitting biological transport of oxygen from the blood stream to the mitochondria within cells. When oxygen binds to the heme pocket, purple deoxymyoglobin becomes oxymyoglobin, characterized by a red color. When a water molecule binds to the heme group, the myoglobin molecule turns brown and is referred to as metmyoglobin. The binding of carbon monoxide (CO) can cause a red color similar to that produced by oxygen binding. Nitric oxide (NO) has been described as forming a stable pink color in cured meat.
Prior to the 1960's, animal carcasses were shipped to retailers for dividing into retail-sized portions of meat. In the 1960's, the meat industry went through a revolutionary change when the slaughterer began vacuum packaging smaller pieces of meat (referred to as “primals” and “sub-primals”) and placing them in boxes for shipping long distances to the retailer. This permitted centralizing slaughter operations. Shipping cattle to stockyards near large cities was rendered obsolete (the famous Chicago stockyards were closed in 1971). Stockyards near cities were no longer required and the need to ship live cattle long distances was greatly reduced. The retailer then prepared and packaged the fresh meat products as they were sold to consumers at the site of final sale. Such boxed meat had economic advantages: Freight for shipping bones and fat to the retailer and back to the slaughterer was eliminated; labor became more efficient under the production oriented atmosphere of the slaughterer; drip losses from aging and shipping whole carcasses were reduced; and product protection, sanitation and shelf life were improved. These advantages more than offset the additional costs of packaging. This method of shipping boxed meat from the slaughterer to the retailer for the retailer to prepare and package for the consumer still continues in some forms today.
However, the practice of boxing meat and shipping to the retailer may inadequately preserve favorable meat color. The conventional packaging format used by the retail grocer for fresh meat involves stretching a thin plastic film around a foam tray supporting the product. The film is permeable to oxygen so that the color of the meat quickly blooms to a bright red. However, once packaged, meat has a display-case life of only a few days, as the red color of the oxymyoglobin becomes the brown color of the metmyoglobin within approximately three days. Thus, the color often becomes unacceptable before the packaged meat is sold even though the meat remains nutritious, tasty and healthy for consumption. The unacceptability of the color results in meat not being sold and in unnecessary wastes of meat, packaging materials and slaughtered animals.
As a result, packaging formats that promote and maintain fresh meat color for a longer period of time are needed for centralized packaging operations. One attempted approach is to package meat in oxygen barrier, vacuum bags. These bags are vacuum sealed and prevent oxygen contact with the meat until the package is opened. Vacuum sealed meat products are nutritious, healthy, have a long shelf life and are less prone to freezer burn. However, they also may have an undesirable purple meat color that does not bloom to a desirable red color until the meat is exposed to air. Consumer acceptance of meat having a purple color is less than that of meat having a red color. In the mid-1 980's, Excel Corporation and The Kroger Company developed a program to market a flexible vacuum package of Excel's case-ready beef cuts. The vacuum package resulted in a purple meat color. The program failed because the majority of consumers would not accept the purple color.
To provide meat with the consumer preferred red color, meat has also been packaged in a case-ready, modified atmosphere package (“MAP”). Case-ready meat products can be generally defined as fresh meat that is prepackaged and optionally prelabeled at a centralized location and delivered to the retail market prepared for final sale. Increasingly, meat products such as ground beef, turkey and chicken products delivered to U.S. domestic supermarkets for retail sale are delivered in case-ready packaging. For many supermarkets, especially so-called “mega-grocery stores,” case-ready meat products provide not only cost savings in terms of minimizing or eliminating on-site butchering and packaging, but also increased sanitation and decreased incidence of product spoilage. The case-ready meat product preferably provides a predetermined weight and/or volume of a common meat product, such as chicken breast and ground beef. The meat product may be provided fresh, frozen, hard chilled, thawed, enhanced, processed or cooked.
In a case-ready, MAP, the meat is maintained in a sealed pocket containing an atmosphere that is different than ambient air. Various combinations or oxygen, nitrogen and carbon dioxide may be flushed into the package. For example, one such commercially acceptable MAP contains an atmosphere enriched with oxygen (up to 80% by volume) to better maintain a preferred red color. Another case ready MAP maintains meat in carbon dioxide, with very low oxygen content until just before display when the meat is exposed to oxygen to cause blooming to the desired red color. Alternatively, the meat can be contacted with a MAP having an atmosphere containing a small concentration of carbon monoxide (CO) (e.g., 0.4% by volume) to maintain a preferred red meat color. However, while CO-containing MAP may maintain a shelf life comparable to vacuum packaged meat, the red color developed by CO tends to extend through a significant portion of the meat product, causing a permanent “pinking” of the interior of the meat which may remain even after the meat has been fully cooked. The bright red CO-myoglobin complex is referred to as carboxymyoglobin. The presence of carbon monoxide can also disfavorably impact sales of CO-containing MAP packages among consumers.
MAP also requires a headspace for contact of the modified atmosphere with the meat surface to affect the desired color over time. This requirement for a headspace leads to increased package volume, transportation costs and storage requirements and also limits the display appearance by making the product less visible due to the high side walls of the container and the gap between the film and the meat surface.
Nitrite or nitrate salts, such as sodium nitrite, are often used in curing meat, and can also affect meat color. Nitrate and nitrite additives are generally recognized as safe for use in foods, and are commonly known preservatives used in the curing process for products such as hams, lunchmeat, bologna and hot dogs. Nitrite and nitrates are used to cure and disinfect meats in the meat industry often producing a stable pink to red color in the process. For example, GB 2187081A discloses immersion of meat in an aqueous solution of sodium chloride, polyphosphate ions and nitrite ions to preserve meat. See also McGee, On Food and Cooking, Rev. Ed., 2004, “Meat,” Chapter 3, pp. 118-178 (Scribner, New York, N.Y.) which is hereby incorporated by reference. The presence of oxygen can oxidize available nitric oxide to nitrite thus reducing its availability to associate with the myoglobin molecule.
Packaging films have been described that comprise nitrite or nitrate compounds as a desiccant, a food preservative or as a volatile corrosion inhibitor for packaging of metal products. Anti-fungal agents including food preservatives such as sodium nitrite may be applied on various types of packaging to preserve biodegradable packaging against premature deleterious attack by fungi, as disclosed in JP7-258467A. Oxygen barrier films for packaging food products can contain a nitrate salt as a moisture-absorbing agent within an EVOH barrier material or other layer of a multilayer film, as disclosed in JP5-140344A, and U.S. Pat. No. 4,407,897 (Farrell et al.); U.S. Pat. No. 4,425,410 (Farrell et al.); U.S. Pat. No. 4,792,484 (Moritani); U.S. Pat. No. 4,929,482 (Moritani et al.); U.S. Pat. No. 4,960,639 (Oda et al.), and U.S. Pat. No. 5,153,038 (Koyama et al.). Nitrate or nitrite products have also been described as being included in packaging films to absorb moisture, e.g., to inhibit corrosion of metal products, as disclosed in U.S. Pat. No. 2,895,270 (Blaess); U.S. Pat. No. 5,715,945 (Chandler); U.S. Pat. No. 5,894,040 (Foley et al.); U.S. Pat. No. 5,937,618 (Chandler); U.S. Pat. No. 6,465,109 (Ohtsuka), and U.S. Pat. No. 6,942,909 (Shirrell et al.), U.S. Published Patent Application No. 2005/0019537 (Nakaishi et al.), GB Patent No. 1,048,770 (Canadian Technical Tape, Ltd.), and EP Patent Nos. EP 0 202 771 B1 (Aicello Chemical Co. Ltd.), and EP 0 662 527 B1 (Cortec Corp.) and EP 1 138 478 A2 (Aicello Chemical Co. Ltd.). None of these barrier films teach a food-contact portion comprising a nitrite or nitrate material adapted to maintain a desirable appearance of a myoglobin-containing food product.
Current methods of distributing or commercializing myoglobin-containing food products such as fresh meat include many disadvantages in their attempts to maintain a desirable appearance of the food product. What is needed is a new method of distributing such food products, such as methods allowing for a food packaging article to contact a portion of the food product while still achieving a desirable appearance of the surface of the food product for a longer display-life.